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 * Copyright (c) 2008, 2010, Oracle and/or its affiliates. All rights reserved.
 *
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 * modification, are permitted provided that the following conditions
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 *
 *   - Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *
 *   - Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *
 *   - Neither the name of Oracle nor the names of its
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
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 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package controller.util;

import static java.nio.file.StandardWatchEventKinds.ENTRY_CREATE;
import static java.nio.file.StandardWatchEventKinds.OVERFLOW;

import java.io.File;
import java.io.IOException;
import java.nio.file.FileSystems;
import java.nio.file.Path;
import java.nio.file.WatchEvent;
import java.nio.file.WatchKey;
import java.nio.file.WatchService;
import java.util.HashMap;
import java.util.Map;

/**
 * Example to watch a directory (or tree) for changes to files.
 */

public class WatchDir<T> {

	private final WatchService watcher;
	private final Map<WatchKey, Path> keys;
	// private final boolean recursive;
	private boolean trace = false;

	@SuppressWarnings("unchecked")
	static <T> WatchEvent<T> cast(WatchEvent<?> event) {
		return (WatchEvent<T>) event;
	}

	/**
	 * Register the given directory with the WatchService
	 */
	private void register(Path dir) throws IOException {
		// WatchKey key = dir.register(watcher, ENTRY_CREATE,
		// ENTRY_DELETE,ENTRY_MODIFY);
		WatchKey key = dir.register(watcher, ENTRY_CREATE);

		if (trace) {
			Path prev = keys.get(key);
			if (prev == null) {
				System.out.format("register: %s\n", dir);
			} else {
				if (!dir.equals(prev)) {
					System.out.format("update: %s -> %s\n", prev, dir);
				}
			}
		}
		keys.put(key, dir);
	}


	/**
	 * Creates a WatchService and registers the given directory
	 */
	public WatchDir(Path dir/* , boolean recursive */) throws IOException {
		this.watcher = FileSystems.getDefault().newWatchService();
		this.keys = new HashMap<WatchKey, Path>();
		register(dir);
		this.trace = true;
	}

	/**
	 * Process all events for keys queued to the watcher
	 */
	public void processEvents(FileEventHandler<T> handler) {
		//final ArrayBlockingQueue<T> retArray = new ArrayBlockingQueue<>(100);
		new Thread(()->{
		while(true) {

			// wait for key to be signalled
			WatchKey key=null;
			try {
				key = watcher.take();
			} catch (InterruptedException x) {
			}

			for (WatchEvent<?> event : key.pollEvents()) {
				WatchEvent.Kind<?> kind = event.kind();

				// TBD - provide example of how OVERFLOW event is handled
				if (kind == OVERFLOW) {
					continue;
				}

				// Context for directory entry event is the file name of entry
				WatchEvent<Path> ev = cast(event);
				Path name = ev.context();
//				Path child = dir.resolve(name);

				// print out event
				// System.out.format("%s: %s\n", event.kind().name(), child);
				if (handler != null) {
					handler.processReceivedFile(name.toFile());
				}
			}

			// reset key and remove from set if directory no longer accessible
			boolean valid = key.reset();
			if (!valid) {
				keys.remove(key);

				// all directories are inaccessible
				if (keys.isEmpty()) {
					break;
				}
			}
		}
		}).start();
		
		//return retArray;
	}



	public interface FileEventHandler<T> {
		T processReceivedFile(File inFile);
	}
	

	public static void main(String[] args) throws IOException {
		// parse arguments
		Path path = FileSystems.getDefault().getPath("input");

		// new WatchDir(dir, recursive).processEvents();
		 new WatchDir<String>(path).processEvents((f) -> {
			System.out.println("allo this is the file " + f.toString());
			return new String("sdsf");
		});
	}
}